Oracle Database Error Solutions & DBA Guide

ORA-00904: Invalid Identifier – Complete Oracle DBA Troubleshooting Guide The ORA-00904: invalid identifier error is one of the most common SQL errors encountered in Oracle Database. It affects Oracle Database Administrators (DBAs), SQL developers, PL/SQL developers, Oracle Forms developers, Oracle APEX developers, Oracle E-Business Suite administrators, ETL developers, reporting teams, and application support engineers. ORA-00904 occurs when Oracle encounters a column name, alias, object attribute, or identifier that it cannot recognize during SQL parsing. While many administrators assume the column does not exist, the actual root cause is often more complex and may involve case-sensitive identifiers, quoted column names, invalid aliases, incorrect schema references, dynamic SQL, editioning, or application deployment issues. Before Oracle executes a SQL statement, it validates every referenced identifier against the database dictionary. If Oracle cannot resolve a refere...

ORA-00060: Deadlock Detected While Waiting for Resource – Complete Oracle DBA Troubleshooting Guide The ORA-00060: deadlock detected while waiting for resource error is one of the most important Oracle Database concurrency errors encountered in production environments. It occurs when two or more database sessions become trapped in a circular locking dependency, where each session is waiting for a resource held by another session. Because none of the sessions can proceed, Oracle automatically detects the deadlock and resolves it by terminating one of the conflicting SQL statements. Unlike ordinary blocking situations, where one session simply waits for another to complete, a deadlock creates a circular dependency that cannot resolve itself. Oracle's deadlock detection mechanism identifies the cycle, selects one statement as the victim, rolls back only that statement, and allows the remaining transaction to continue. ORA-00060 is commonly encountered in OLTP applicatio...

ORA-00257: Archiver Error. Connect AS SYSDBA Only Until Resolved – Complete Oracle DBA Troubleshooting Guide The ORA-00257: Archiver Error. Connect AS SYSDBA Only Until Resolved error is one of the most common Oracle Database production errors encountered by Database Administrators (DBAs). This error indicates that Oracle can no longer archive online redo logs because the archive destination has become unavailable or full. As a result, normal database users are prevented from establishing new connections until the archiving issue is resolved. Oracle databases running in ARCHIVELOG mode rely on archived redo logs for media recovery, point-in-time recovery, Oracle Data Guard synchronization, RMAN backups, and disaster recovery. When Oracle cannot archive a redo log, the database eventually stops processing new transactions to protect recoverability. Although ORA-00257 most frequently occurs because the Fast Recovery Area (FRA) is full, it may also be caused by a full fil...

ORA-28040: No Matching Authentication Protocol – Complete Oracle Database Troubleshooting Guide The ORA-28040: No Matching Authentication Protocol error is one of the most common authentication issues encountered after upgrading an Oracle Database, Oracle Client, or middleware application. It typically appears when an older client attempts to connect to a newer Oracle database that no longer supports legacy authentication protocols. This guide explains everything you need to know about the ORA-28040 error, including its causes, how Oracle authentication works, troubleshooting techniques, multiple solutions, best practices, and preventive measures. Whether you are an Oracle DBA, System Administrator, Developer, or Infrastructure Engineer, this article provides a practical, production-ready approach to resolving the issue safely. What is ORA-28040? The ORA-28040 error indicates that the authentication protocol used by the Oracle client is not compatible with the authenticat...